A prior art light emitting diode (LED) die 10 in the form of a vertical light emitting diode (VLED) die is shown in FIGS. 1A-1C. As shown in FIG. 1A, the light emitting diode (LED) die 10 includes a substrate 12, and an epitaxial stack 14 on the substrate 12. The epitaxial stack 14 includes an n-type semiconductor layer 16, a multiple quantum well (MQW) layer 18 in electrical contact with the n-type semiconductor layer 16 configured to emit electromagnetic radiation, and a p-type semiconductor layer 20 in electrical contact with the multiple quantum well (MQW) layer 18; the n-type semiconductor layer 16 could have multilayers of various n-type doping including lightly doped layer (sometime is called undoped layer) or buffered layer and may also have super lattice layer/layers; the p-type semiconductor layer 16 could have multilayers of various p-type doping level and electron blocking layer (EBL); it is well known that the MQW layer 18 is comprised of many pairs of well and barrier layers. The light emitting diode (LED) die 10 also includes a mirror layer 22, a p-contact layer 24 in electrical contact with the p-type semiconductor layer 20, and a p-pad 28 in electrical contact with the p-contact layer 24.
The light emitting diode (LED) die 10 also includes an n-pad 30 comprised of multiple conductive n-trenches 25 in electrical contact with n-conduct areas 27 on the n-type semiconductor layer 16. The light emitting diode (LED) die 10 also includes an electrical insulator layer 26 configured to electrically isolate the p-pad 28 and the n-pad 30. As shown in FIG. 2, during a packaging process, the light emitting diode (LED) die 10 can be flip chip mounted to a module substrate 32 with the p-pad 28 bonded to a p-electrode 34 on the module substrate 32, and with the n-pad 30 bonded to an n-electrode 36 on the module substrate 32.
One characteristic of the light emitting diode (LED) die 10 is that the p-pad 28 and the n-pad 30 are separated by a gap WGAP. The size of the gap WGAP affects the output radiation of the light emitting diode (LED) die 10, particularly along the outside edge of the p-pad 28. For example, if the gap WGAP is relatively large, then the distance between the p-pad 28 and the n-pad 30 would also be large, and the output radiation along the outside edge of the p-pad 28 would be low. The width WP-PAD of the p-pad 28 is also dependent on the size of the gap WGAP, such that a smaller p-pad width WP-PAD also produces a lower output radiation. The size of the gap WGAP, along with the p-pad width WP-PAD and the n-pad width WN-PAD, are set by the fabrication process, such that additional masks and additional process steps, are required to vary the dimensions of these features.
It would be desirable for the gap WGAP to be adjustable to permit optimization of the radiation output of the light emitting diode (LED) die 10, particularly along the outside edge of the p-pad 28. In addition, an adjustable size for the gap WGAP would allow the p-pad width WP-PAD, and the n-pad width WN-PAD to be optimized. Further, an adjustable gap WGAP would facilitate the packaging process by permitting flexibility in the alignment of the p-pad 28 and the n-pad 30 to the electrodes 34, 36 on the module substrate 32. The present disclosure is directed to a light emitting diode (LED) die having n-straps that permit the size of the gap WGAP, as well as the p-pad width of the width WP-PAD and the n-pad width WN-PAD to be adjusted to provide optimal radiation output, and a large process window for packaging.
However, the foregoing examples of the related art and limitations related therewith are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification and a study of the drawings. Similarly, the following embodiments and aspects thereof are described and illustrated in conjunction with a light emitting diode (LED) die which are meant to be exemplary and illustrative, not limiting in scope.